The present invention relates generally to blast aerator technology of the type adapted to insure the flow of bulk materials within bins, hoppers or the like. More particularly, the present invention is concerned with a multiple blast aerator system which is appropriately timed to induced seqential detonation of the aerators to promote bulk material transfer.
It is well known that in handling or processing bulk materials such as cement, coal, wood chips or the like the hoppers or storage bins employed often become jammed or temporarily blocked. Such materials may tend to cake or congeal during bulk processing, particularly with the natural phenomenon of first in last out flow of a single discharge hopper. Previously it has been suggested to remedy bulk flow problems by physically vibrating the hopper or container to shake materials loose, but not all materials may be dislodged in this manner. For example, large concrete bunkers may be impossible to vibrate. Furthermore, some materials like soft wood chips ordinarily absorb vibratory energy and must be dislodged by other methods.
Various phenomena occur during the processing of bulk materials through conventional conically shaped hoppers. For example, bridges or arches of materials often form, preventing the escape of material above the arch. Often "rat holes" or funnels occur when material immediately above the hopper exits drops through, while remaining material bunches up on top. Particles of material may form cohesive bonds either by adhesion due to chemical or hydrostatic attraction, or particles may interlock because of horizontal and vertical compression thereof. Also, friction between the massive material stored in the bunker or hopper and the walls thereof tends to prevent proper flowage. Because of these and other phenomena associated with bulk processing, a plurality of air blaster or blast aerator designs have been previously proposed.
Blast aerators periodically introduce a large blast of air into the hopper to dislodge material. The volume of compressed air released by the quick opening valve normally employed with blast aerators strikes the material at a rate of over six hundred feet per second. Materials directly adjacent to or in front of the discharge outlet of the aerator are forcibly dislodged by the impact. When the large volume of air outputted by the aerator enters the bin, the air continues to expand during and after the impact phase of the discharge. This greatly stimulates and disturbs the materials within the hopper. Blast aerators characterized by the foregoing observations may be seen in U.S. Pat. Nos. 3,915,339; 4,197,966; and 3,651,988. Other relevant blast aerator technology may be seen in Great Britain Pat. Nos. 1,426,035 and 1,454,261. Also relevant are West German Patent 2,402,001 and Australian Pat. No. 175,551.
Air blasters are generally more efficient than other methods of dislodging jammed, bulk materials since the force outputted by them is applied directly to the material, rather than to the walls of the structure, as in the case of vibrators. Blasters also have an advantage of impact against the material, which is not available from air slides air wands, and various air screen devices which inject low pressure air into the material. Live bottoms in hoppers or bins are limited in their effectiveness, since they may tend to create bridging or arching of material. However, air blasters are intended for use only as a flow stimulator from materials which are primarily moved by the force of gravity. They are not intended to be the prime movers of material, and should not be used to initiate flow or movement of material when gravity feed is not used.
In operation, the mechanical parts of the aerator will encounter extremely high stresses which tend to promote component failure. For example, piston wear and tear is a large problem. In prior art designs that portion of the piston utilized to create a seal also functions as the working surface upon which tank pressure works to force the piston to its rearward "blast" position. Thus, as explained in my co-pending patent application, Ser. No. 354,310, filed Mar. 03, 1982, and entitled Blast aerator, a dual diameter piston would seem desirable.
Traditionally aerator discharge pipes enter the hopper at a perpendicular angle. This method has several disadvantages. First, material to the rear of the blast aerator discharge orifice may remain unaffected, creating pillars or columns of material which may support arching above the discharge pipes. Also, perpendicular mounting of the blast output pipe results in the formation of tunnels which are forced through the material by the blast. Often the discharged air will escape through the "rat hole" or tunnel which comprises the path of least resistance, rather than dissipating its force by dislodging particles. Thus, it is desirable to avoid dissipation of the air blast within the openings or caverns within the hopper. Moreover, it is desirable to dissipate the blast of the aerator within the materials stored within the hopper to reduce the noise experienced by operating personnel.